Changes of telomere length cause reciprocal changes in the lifespan of mother cells in Saccharomyces cerevisiae

Budding yeast cells divide asymmetrically, giving rise to a mother and its daughter. Mother cells have a limited division potential, called their lifespan, which ends in proliferation-arrest and lysis. In this report we mutate telomerase in Saccharomyces cerevisiae to shorten telomeres and show that, rather than shortening lifespan, this leads to a significant extension in lifespan. This extension requires the product of the SIR3 gene, an essential component of the silencing machinery which binds to telomeres. In contrast, longer telomeres in a genotypically wild-type strain lead to a decrease in lifespan. These findings suggest that the length of telomeres dictates the lifespan by regulating the amount of the silencing machinery available to nontelomeric locations in the yeast genome.     

Prenatal cocaine alters social competition of infant, adolescent, and adult rats

This series of experiments examined whether gestational cocaine exposure alters later social behavior exhibited during competition for biologically relevant stimuli. Rat offspring were derived from dams that received subcutaneous injections of 40 mg/kg/3cc cocaine HCl daily on gestational Days 8-20, pair-fed dams injected with saline, or nontreated control dams. Offspring competed with peers for access to a nipple in infancy, and to water in adolescence or adulthood. Prenatal cocaine exposure resulted in a decreased ability of cocaine-exposed infant rats to compete successfully for a nipple. Although adolescent and adult cocaine-exposed rats were no less successful than controls when competing for water, they exhibited a notable increase in aggression toward competitors during testing. Data provide evidence of alterations in social behavior and social competition as a result of prenatal cocaine exposure.     

Three-dimensional solution structure of alpha-conotoxin MII by NMR spectroscopy: effects of solution environment on helicity

alpha-Conotoxin MII, a 16-residue polypeptide from the venom of the piscivorous cone snail Conus magus, is a potent and highly specific blocker of mammalian neuronal nicotinic acetylcholine receptors composed of alpha3 beta2 subunits. The role of this receptor type in the modulation of neurotransmitter release and its relevance to the problems of addiction and psychosis emphasize the importance of a structural understanding of the mode of interaction of MII with the alpha3 beta2 interface. Here we describe the three-dimensional solution structure of MII determined using 2D 1H NMR spectroscopy. Structural restraints consisting of 376 interproton distances inferred from NOEs and 12 dihedral restraints derived from spin-spin coupling constants were used as input for simulated annealing calculations and energy minimization in the program X-PLOR. The final set of 20 structures is exceptionally well-defined with mean pairwise rms differences over the whole molecule of 0.07 A for the backbone atoms and 0.34 A for all heavy atoms. MII adopts a compact structure incorporating a central segment of alpha-helix and beta-turns at the N- and C-termini. The molecule is stabilized by two disulfide bonds, which provide cross-links between the N-terminus and both the middle and C-terminus of the structure. The susceptibility of the structure to conformational change was examined using several different solvent conditions. While the global fold of MII remains the same, the structure is stabilized in a more hydrophobic environment provided by the addition of acetonitrile or trifluoroethanol to the aqueous solution. The distribution of amino acid side chains in MII creates distinct hydrophobic and polar patches on its surface that may be important for the specific interaction with the alpha3beta2 neuronal nAChR. A comparison of the structure of MII with other neuronal-specific alpha-conotoxins provides insights into their mode of interaction with these receptors.     

Analysis of the immunologic heterogeneity of HIV-1: I. "Arginine-glutamine trigger" in the fourth position of the central tetrapeptide of the V3 loop of gp120

This article reviews the existing knowledge base concerning the biology of spinal fusion, with the understanding that the focus is weighted toward posterolateral lumbar spinal fusion because of a relative paucity of biologic information on healing of other types of fusions. The discussion focuses first on the basic science of spinal fusion healing from the standpoint of animal modeling. Next, the discussion centers on the multitude of local factors that can affect fusion healing. Finally, the numerous systemic factors known to affect fusion healing are discussed.     

Increased immune activation precedes the inflection point of CD4 T cells and the increased serum virus load in human immunodeficiency virus infection

In sickness-conditioned learning, animals become ill after sampling a new substance and develop an aversion that is expressed as avoidance of that substance in subsequent presentations. We examined the parameters of a one-trial, nongustatory, sickness-conditioned learning task in day-old chicks. Chicks pecked a bead and were made ill by i.p. injection of lithium chloride (LiCl). Both 0.5 and 1.0 M LiCl (0.1 ml) produced reliable avoidance at test. Chicks injected with LiCl between 15 and 45 min after training avoided the bead at test, whereas those injected within 5 or 10 min or more than 45 min after training did not. Avoidance was present until 24 h posttraining and absent after 48 h. Therefore, robust learning of the sickness-conditioned learning task occurs in one trial without the need for gustatory cues, and memory for the task lasts at least 24 h. Uses of this task to study memory formation in the day-old chick are discussed.     

Time-course of the uterine response to estradiol-17beta in ovariectomized ewes: expression of angiogenic factors

Uterine expression of angiogenic factors (vascular endothelial growth factor [VEGF] and basic fibroblast growth factor [bFGF]) was evaluated in ovariectomized ewes at 0, 2, 4, 8, 24, 48, or 72 h after estradiol (E2) treatment. Endometrial VEGF mRNA increased more than 5-fold from 0 to 4 h, remained elevated at 8 h, and then declined through 72 h after E2 treatment. In contrast, endometrial bFGF mRNA remained constant from 0 to 4 h, increased 2.2-fold from 4 to 8 h, remained elevated at 24 h, and then declined through 72 h. Immunostaining for VEGF was present in myometrial and endometrial microvessels (arterioles, venules, and/or capillaries) and also in myometrial smooth muscle; the pattern of VEGF immunostaining followed that of mRNA expression, being elevated at 4 and 8 h after E2 treatment. Immunostaining for bFGF was present exclusively in uterine glands; the pattern of bFGF immunostaining also followed that of its mRNA, being elevated at 8 and 24 h after E2. On the basis of these observations, we suggest that VEGF and bFGF are probably important factors responsible for the dramatic uterine microvascular response that occurs 8 to 24 h after E2 treatment in ovariectomized ewes.     

Nutritional intervention and growth in children with chronic renal failure

During fifties there were at most few tens of persons in this country who believed in the future of computers and cybernetics. One group of such enthusiasts, headed by Antonín Svoboda, was working at a construction of the first Czech computer SAPO. The other group tried to analyse, anticipate, and prepare in advance various applications for the new systemic conceptions and for the information processing machines. Members of both groups met for discussions which opened prospects to the future and influenced many of other activities for a long time. At the early sixties, the Czechoslovak Cybernetic Society was established at the Czechoslovak Academy of Sciences and in 1962 the Main Problem Committee for the Medical Cybernetics was founded at the Department of Health. It coordinated majority of the research programmes in the medical cybernetics and informatics. In 1967-1969 the Committee prepared an extensive project of a medical information system (ZIS), but its accomplishment was finally blocked by the then authorities. However, interests for that topics kept growing and the new working places equipped with available computer technology were formed at the health and clinical centres. The first tentative lectures in medical cybernetics and biocybernetics at our faculty were introduced into the students curricula in the late sixties. Thematically, medical cybernetics subsequently differentiated into the medical informatics, simulations of biological and medical systems, and the biosignal analysis. The growing interest enabled to hold conferences since the middle of seventies, some of which were held periodically, sometimes with international participation. It is not possible in brevity to include the whole spectrum to those goal-directed activities nor to appraise adequately their future significance.     

p53 and thymidylate synthase expression in untreated stage II colon cancer: associations with recurrence, survival, and site

We initiated a retrospective study to determine whether p53 status and thymidylate synthase (TS) protein expression in primary colon tumors influence recurrence and survival for patients with stage II colon cancer. Tumor specimens from 45 consecutive untreated patients with stage II colon cancer were examined for p53 and TS protein expression using immunohistochemistry. The median follow-up was 5.1 years. Eighteen patients had left-sided tumors, and 27 had right-sided tumors. Fourteen of 45 patients (31%) developed recurrence. p53 overexpression was detected in the tumors of 18 patients (40%); 10 patients (55%) with p53 overexpression recurred; and 4 of 27 (15%) without evidence of p53 overexpression recurred (P = 0.002). High TS expression was detected in the tumors of 16 patients (36%): 8 patients (50%) with high TS expression recurred, and 6 patients (21%) with low TS expression recurred (P = 0.027). Patients with p53 overexpression had a significantly poorer survival than did those patients without p53 overexpression (P < 0.001). High TS expression was associated with poor survival (P = 0.004). p53 overexpression and high TS expression were significantly associated with left-sided tumors (P = 0.003 and P = 0.022). Thirteen of 16 patients (81%) with high TS expression also overexpressed p53, and 24 of 29 patients (81%) with low TS expression did not manifest p53 overexpression (P < 0.001). p53 and TS expression in primary stage II colon cancer are associated and appear to influence recurrence and survival. In this pilot study, left-sided tumors demonstrate significantly more p53 overexpression and significantly higher TS expression than do right-sided tumors, which may explain the significantly poorer survival for patients with left-sided tumors.     

Molecular beacon sequence analysis for detecting drug resistance in Mycobacterium tuberculosis

Strictureplasty for treatment of symptomatic intestinal strictures secondary to Crohn's disease is being performed with increasing frequency. To determine the overall clinical results after strictureplasty for Crohn's disease, all patients undergoing this procedure were prospectively studied. Between 6/1/89 and 2/1/97, 57 Crohn's disease patients underwent 60 operations utilizing strictureplasties. A total of 109 strictureplasties were performed (90 Heineke-Mikulicz, 6 Finney, and 13 side-to-side isoperistaltic). The 30-day perioperative morbidity was 12%, with complications being less common for patients undergoing elective versus unscheduled operations (p < 0.002). Recurrence of Crohn's disease requiring operation was seen in seven patients after a mean follow-up of 38 months. The estimated cumulative recurrence rate after 2 years was 15 +/- 6% (+/- standard error) and 22 +/- 10% at 5 years. A recurrence developed at the site of the previous strictureplasty in only five cases. Strictureplasty is a safe, effective means of providing long-term surgical palliation to selected patients with Crohn's disease. Perioperative complication rates are comparable to those seen with standard surgical treatment, and recurrences are not excessive.